1. Field of the Invention
The present disclosure relates to an intake manifold for introducing air into an engine, in particular, an intake manifold capable of reducing flow noise generated between a throttle valve and a surge tank.
2. Description of the Related Art
An automobile has an intake manifold for introducing air into an engine. The intake manifold is connected with a throttle valve apparatus located at an upstream side of the intake manifold. The throttle valve is opened and closed in order to control incoming airflow.
The intake manifold generally has a surge tank for receiving air taken by the throttle valve apparatus. In a state that negative pressure, i.e., pressure less than that of the air taken by the throttle valve apparatus, is kept in the surge tank of this intake manifold, when the throttle valve apparatus is opened, the air flows into the surge tank in bursts. The air flowing into the surge tank eddies downstream of the throttle valve apparatus, and thus generates high-frequency noise. This noise is so called as “shupo-on”, and sound volume of the noise tends to increase in a state that the surge tank is constructed by resin.
Japanese Laid-Open Patent Publication No. 11-141420 discloses a net located near the throttle valve apparatus in an air intake pathway from the throttle valve apparatus to the surge tank, i.e., downstream of the throttle valve apparatus, for decreasing eddy of the air, thereby reducing the noise.
There has been a need in the art for an improved intake manifold.